1. Field of the Invention
The present invention relates to a thin-film magnetic head for applying to a magnetic recording technique, especially to a tape head for reading data from a magnetic tape and writing data to the tape. The present invention further relates to a magnetic tape apparatus provided with the tape head.
2. Description of the Related Art
In recent years, magnetic recording and reproducing apparatuses have been remarkably improved in capacity of storage data. And magnetic tape apparatuses for backing up or storing data are no exception of this trend of larger capacity, and have been required to be improved in areal recording density and to have multichannel configuration, corresponding to the larger capacity.
Thin-film magnetic heads, which are widely used for the above-described magnetic recording and reproducing apparatuses, write data to a magnetic recording medium and read data from the medium. The thin-film magnetic heads have also been strongly required to be miniaturized and to be improved in performance, corresponding to the larger capacity. For example, the thin-film magnetic head for the magnetic tape apparatus (tape head) includes a read head part and a write head part in which a plurality of read head elements and write head elements are aligned along the track width direction, respectively, in order to realize the multichannel configuration and to perform read and write operations to multiple tracks.
As a result, especially in some cases of such tape heads, the read head elements are likely to interact with one another to cause a negative effect on their read characteristics. For example, a magnetoresistive (MR) element, which is usually used as a read head element, has shield layers for shielding an MR multilayer that is a magneto-sensitive portion from external magnetic fields as a noise. The shield layers are required to have a stable magnetic-domain structure in order to obtain adequate resistance changes according to signal magnetic fields during read operation. However, in some cases that the shield layers come close to each other corresponding to the multichannel configuration, a required stable magnetic-domain structure is likely not to be obtained due to the interference among magnetic-domains of individual shield layers. In this occasion, the problem such as a noise in the read output or an insufficient read output is likely to occur.
As a measure for stabilizing the magnetic-domain structure of the shield layers, there is a configuration in which the MR elements are sufficiently distant from each other. However, such a configuration cannot meet the trend of smaller track pitch according to the above-described improvement in areal recording density and multichannel configuration. As another measure, for example, Japanese Patent Publication No. 9-16910A describes a head assembly, in which one common magnetic pole is used instead of the lower magnetic poles of a plurality of heads, and further shields are provided between the heads. However, in some cases that one common shield layer is provided instead of a plurality of upper or lower shield layers as an application of the just-described technique, a cross-talk between the adjacent MR elements or an electrostatic discharge between upper and lower shield layers has a possibility to occur. The electrostatic discharge to break the elements have a potential to occur in the case that the opposed area of the upper and lower shield layers becomes larger as the area of each shield layer becomes larger. Further, the common shield layer has a closure magnetic-domain structure as a whole. As a result, formed are magnetic domains in both end portions in the track width direction, each of which has a magnetization with a direction in-plane and perpendicular to the track width direction. Such magnetic domains are likely to cause a noise in the read output or an unstable output.